<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div div div div div div div div div div h1 {
            color: red;
        }
        .h1 {
            color: green;
        }
        #h1 {
            color: blue;
        }
    </style>
</head>
<body>
    <div>
        <div>
            <div>
                <div>
                    <div>
                        <div>
                            <div>
                                <div>
                                    <div>
                                        <div>
                                            <h1  class="h1">hello world3</h1>
                                        </div>
                                    </div>
                                </div>
                            </div>
                        </div>
                    </div>
                </div>
            </div>
        </div>
    </div>
    <h1>hello world1</h1>
    <h1 class="h1">hello world2</h1>
    <h1 id="h1" class="h1">hello world3</h1>
</body>
</html>